Direct neuronal conversion of microglia/macrophages reinstates neurological function after stroke

Ischaemic brain injury causes permanent neuronal loss, which often results in persistent severe neurological dysfunctions. Although generating new neurons in the injured brain would be an ideal approach to replenish the lost neurons for repairing the damage, the adult mammalian brain retains only limited neurogenic capability. Here, we show that direct conversion of microglia/macrophages into neurons in the brain has great potential as a therapeutic strategy for ischaemic brain injury. After transient middle cerebral artery occlusion in adult mice, microglia/macrophages converge at the lesion core of the striatum, where neuronal loss is prominent. Targeted expression of a neurogenic transcription factor, NeuroD1, in microglia/macrophages in the injured striatum enables their conversion into induced neuronal cells that functionally integrate into the existing neuronal circuits. Furthermore, NeuroD1-mediated induced neuronal cell generation significantly improves neurological function in the mouse stroke model, and ablation of these cells abolishes the gained functional recovery. Our findings thus demonstrate that neuronal conversion contributes directly to functional recovery after stroke and shed further light on the development of therapies for ischaemic brain injury by in situ neuronal conversion technology.

Cend1 and Neurog2 efficiently reprogram human cortical astrocytes to neural precursor cells and induced-neurons

Direct reprogramming of glial cells into induced-neurons is a promising strategy for CNS repair after acute injury or neurodegenerative diseases. Grey matter astrocytes, which exhibit features of neural stem cells when activated, are an ideal cell source for direct neuronal conversion. Aim of the study is the investigation of the neuronal reprogramming capacity of CEND1 and/or Neurogenin-2 (NEUROG2) upon their overexpression on primary human adult cortical astrocytes. Our data indicate that adult human cortical astrocytes can be directly reprogrammed by either CEND1 or NEUROG2 to cells with differentiated neuronal morphology, exhibiting long neurites and branched processes. Exploration of gene expression dynamics along the conversion process revealed that neuronal genes are significantly up-regulated while astrocytic genes are down-regulated. Differentiated induced-neurons (iNs) exhibit either GABAergic or glutamatergic/dopaminergic identity upon CEND1 and NEUROG2 overexpression respectively. Co-expression of CEND1 and NEUROG2 in double-transduced cultures induced elevated expression levels of neural progenitor/stem genes and appearance of highly proliferative spheres with neural progenitor cell (NPC) properties in culture.

Transcription factor-based gene therapy to treat glioblastoma through direct neuronal conversion

Glioblastoma (GBM) is the most prevalent and aggressive adult primary cancer in the central nervous system (CNS). Therapeutic approaches for glioblastoma are under intense investigation, such as the emerging immunotherapy, but so far only marginal progress has been made due to the heterogeneity and highly invasive nature of glioblastoma. Here, we propose an alternative approach to tackle GBM through reprogramming proliferative GBM cells into non-proliferative neurons. We report efficient neuronal conversion from human GBM cells by overexpressing single neural transcription factor Neurogenic differentiation 1 (NeuroD1), Neurogenin-2 (Neurog2) or Achaete-scute homolog 1 (Ascl1). Subtype characterization reveals that the majority of Neurog2- and NeuroD1-converted neurons are glutamatergic, while Ascl1 favors GABAergic neuron generation. The GBM cell-converted neurons not only express pan-neuronal markers, such as NeuN and MAP2, but also exhibit neuron-specific electrophysiological activities. We further conducted transcriptome analyses to investigate the underlying cell conversion mechanism. Our RNA-seq analyses discover that neuronal genes are activated among glioma cells after overexpression of neural transcription factors, and different signaling pathways are activated by different neural transcription factors. Importantly, the neuronal conversion of GBM cells is accompanied by significant inhibition of GBM cell proliferation in both in vitro and in vivo models. Therefore, these results suggest that GBM cells can be reprogrammed into different subtypes of neurons, leading to a potential alternative approach to treat brain tumor.SignificanceConverting dividing glioblastoma cells into non-dividing neurons may provide an innovative therapeutic approach to treat glioblastoma.HighlightsEfficient neuronal conversion of human glioblastoma cells achieved by overexpression of neural transcription factorsNeurog2- and NeuroD1-converted neurons are mostly glutamatergic, while Ascl1-converted neurons are mainly GABAergicTranscriptome analyses reveal the activation of neuronal genes after overexpression of neural transcription factors in glioblastoma cellsInhibition of cell proliferation during glioblastoma cell conversion both in vitro and in vivo

Different Effects of Cannabis Abuse on Adolescent and Adult Brain

Cannabis abuse is a common phenomenon among adolescents. The dominant psychoactive substance in <i>Cannabis sativa</i> is tetrahydrocannabinol (THC). However, in the past 40 years the content of the psychoactive ingredient THC in most of the preparations is not constant but has increased due to other breeding and culturing conditions. THC acts as the endocannabinoids at CB1 and CB2 receptors but pharmacologically can be described as a partial (not a pure) agonist. Recent evidence shows that activation of the CB1 receptor by THC can diminish the production of neuronal growth factor in neurons and affect other signalling cascades involved in synapsis formation. Since these factors play an important role in the brain development and in the neuronal conversion processes during puberty, it seems reasonable that THC can affect the adolescent brain in another manner than the adult brain. Accordingly, in adolescent cannabis users structural changes were observed with loss of grey matter in certain brain areas. Moreover, recent studies show different effects of THC on adolescent and adult brains and on behaviour. These studies indicate that early THC abuse can result in neuropsychological deficits. This review gives an overview over the present knowledge in this field.

Reversing Glial Scar Back To Neural Tissue Through NeuroD1-Mediated Astrocyte-To-Neuron Conversion

ABSTRACTNerve injury often causes neuronal loss and glial proliferation, disrupting the delicate balance between neurons and glial cells in the brain. Recently, we have developed an innovative technology to convert internal reactive glial cells into functional neurons inside the mouse brain. Here, we further demonstrate that such glia-to-neuron conversion can rebalance neuron-glia ratio and reverse glial scar back to neural tissue. Specifically, using a severe stab injury model in the mouse cortex, we demonstrated that ectopic expression of NeuroD1 in reactive astrocytes significantly reduced glial reactivity and transformed toxic A1 astrocytes into less harmful astrocytes before neuronal conversion. Importantly, astrocytes were not depleted after neuronal conversion but rather repopulated due to its intrinsic proliferation capability. Remarkably, converting reactive astrocytes into neurons also significantly reduced microglia-mediated neuroinflammation. Moreover, accompanying regeneration of new neurons together with repopulation of new astrocytes, blood-brain-barrier was restored and synaptic density was rescued in the injury sites. Together, these results demonstrate that glial scar can be reversed back to neural tissue through rebalancing neuron:glia ratio after glia-to-neuron conversion.